Differential ring modulator

A differential optical modulator includes, in part, a splitter splitting an incoming optical signal into first and second input signals, a first variable coupler generating a first differential output signal in response to the first input signal, and a second variable coupler generating a second differential output signal in response to the second input signal. The first variable coupler includes, in part, first and second couplers and a phase shifter disposed therebetween. The first coupler generates a pair of internal signals in response to the first input signal. The second coupler generates the first differential output signal. The second variable coupler includes, in part, third and fourth couplers and a phase shifter disposed therebetween. The third coupler generates a pair of internal signals in response to the second input signal. The fourth coupler generates the second differential output signal.